Solute
Definition
The substance that gets dissolved: the salt in salt water, the sugar in tea.
Technical definition
The solute is the substance dissolved in a solvent to form a solution, typically present in the smaller amount. Its quantity relative to the solvent defines concentration measures such as molarity and molality.
Example
In seawater, sodium chloride is the main solute, at about 35 g per liter.
Common confusion
The solute is not always a solid. In carbonated water, CO2 gas is the solute dissolved in liquid water.